Research On Coal Pillar Width And Support Optimization Of Roadway Driving Along Goaf In Extra-thick Coal Seam

In recent years,the technology of driving along the goaf has been widely used in many mines.Driving along the goaf is the method of mining along the edge of goaf with small coal pillars.Because there will be a large goaf left after the mining of the working face in the upper section,under the action of the stress of the overlying strata,there will be a large range of strata affected by the goaf,and the phenomenon of the pressure of the overlying strata appears from time to time,which makes the majority of scholars And the researchers have a great interest in the control technology of the surrounding rock produced by driving along the goaf.In the research process of this problem,the reasonable setting of coal pillar width is the main topic that can not be avoided.Too wide coal pillar will lead to a large number of coal resource losses.If the width of coal pillar is too narrow,the phenomenon of mine pressure will occur frequently,which will bring a lot of problems to the surrounding rock control and support of the roadway,leading to the normal production of the roadway.In this paper,based on the research background of 30503 working face in Datong Coal Mine Group,some mechanical parameters of coal seam and roof in the working face are surveyed on the spot,and theoretical calculation of the width of coal pillar is carried out by using relevant theoretical knowledge such as mining rock mechanics,etc.,then the stress and displacement of coal pillar with different width are simulated by FLAC3 D,and then a new supporting scheme is proposed to optimize the old supporting scheme,FL is used Ac3 d verifies the feasibility of the new scheme.The main conclusions are as follows:Based on the key layer theory,the distribution characteristics of overlying strata after mining are analyzed,and the basic top position is determined.It is concluded that the lowlevel gravel bearing coarse sandstone near the coal seam is hard rock.Because the coal seam in Tongxin coal mine is thick,and the lower level gravel bearing coarse sandstone directly collapses behind and fails to fill the goaf,the cantilever beam structure is formed at the coal wall after the coal seam is mined The broken block in the distance collapses,while the high hard rock layer far away from the coal seam contains gravel and coarse sandstone.The goaf under it is fully filled,and the masonry beam structure is formed after breaking.The disturbance of the overlying strata to the roadway and coal pillar is analyzed by using the different positions of the basic roof fracture.The analysis shows that when the fracture position of the arc triangle block of the goaf roadway is outside the coal pillar,i.e.the goaf area with large working area above,the disturbance control of the movement subsidence to the goaf roadway coal pillar and surrounding rock goaf roadway is the lowest,and the stability of the roadway roof and surrounding rock is also good.Based on the analysis of the load on the coal pillar,it is concluded that the stress distribution of the wide coal pillar is saddle shape,while the stress distribution of the narrow coal pillar is single peak shape.On this basis,the failure mechanism of the coal pillar and the five failure modes of the coal pillar under the influence of different geological factors are analyzed.Based on the theory of limit equilibrium,the width of plastic zone on one side of goaf and the width of plastic zone on the other side of coal pillar are calculated.The width of plastic zone is 5.0m and 1.72 m respectively.According to the width of the bearing area of the coal pillar,30%-50% of the width of the plastic area should be reached,and the value range of the bearing area calculated is 2.02-3.36 m.Considering the action and stability of coal pillar,the width of coal pillar is determined to be 10 m.On the basis of the front theoretical calculation,the coal pillar width is divided into 6 m,8 m,10 m,12 m,14 m and 16 m for numerical simulation respectively.By comparing and analyzing the distribution of vertical stress,horizontal stress,vertical displacement,horizontal displacement and plastic zone under different coal pillar width,the optimal width of coal pillar is 10 m.Increase the length and diameter of the bolt to increase the strength and range of the bolt,reduce the row spacing between the bolts and enhance the interaction between the bolts.Through the improvement of the original support scheme,the asymmetric support scheme is proposed,and the feasibility of the new and old support schemes is compared and analyzed by using the numerical simulation software.The new support scheme is in stress,displacement and plastic area It has obvious improvement and good supporting effect.